Polyesters and polyamides are both widely used thermoplastic injection molding materials. Compatible blends of these polymers would be very useful since they would allow a designer to develop materials with specific properties in areas such as strength, toughness, chemical resistance and cost. Polyester/polyamide blends are generally incompatible, however, as evidenced by low impact strengths. Low impact strengths preclude the use of these blends in many large, structural parts. While impact modifiers well known in the art may be used to improve impact strength, they generally do not improve the impact strengths of polyester/polyamide blends. In particular, blends of polyamides and copolyesters based on terephthalic acid, ethylene glycol, and cyclohexanedimethanol are not usually used for injection molding applications since they usually have low impact strengths.
Other attempts have been made to improve the impact strengths of polyester/polyamide blends. For example, U.S. Pat. No. 4,812,534 describes the use of a copolyesteramide in minor amounts for improvement of the impact strength of polyester/polyamide blends. Also, D. Gilmore, J. Kirkpatrick, and M. J. Modic describe the use of mixtures of unmodified and maleated styrene-ethylene/butylene-styrene (SEBS) rubbers in Nylon 6, Nylon 66, polyphenylene-ether/propylene blends, polyphenylene-ether-Nylon 66 blends and polypropylene/Nylon 66 blends to improve impact strength as reported in Proceedings of ANTEC, (1990), pp. 1228-1233.